ey, by the diversity, the variety, and the thoroughness of his
investigations, was enabled to give an entirely new direction to at
least two branches--and two of the most important branches--of what
now-a-days we call Biological Science. On the one hand, he founded
all our modern physiology by the discovery of the exact nature of the
motions of the heart, and of the course in which the blood is propelled
through the body; and, on the other, he laid the foundation of that
study of development which has been so much advanced of late years, and
which constitutes one of the great pillars of the doctrine of evolution.
This doctrine, I need hardly tell you, is now tending to revolutionise
our conceptions of the origin of living things, exactly in the same
way as Harvey's discovery of the circulation in the seventeeth century
revolutionised the conceptions which men had previously entertained with
regard to physiological processes.

It would, I regret, be quite impossible for me to attempt, in the course
of the time I can presume to hold you here, to unfold the history of
more than one of these great investigations of Harvey. I call them
"great investigations," as distinguished from "large publications." I
have in my hand a little book, which those of you who are at a great
distance may have some difficulty in seeing, and which I value very
much. It is, I am afraid, sadly thumbed and scratched with annotations
by a very humble successor and follower of Harvey. This little book is
the edition of 1651 of the 'Exercitationes de Generatione'; and if you
were to add another little book, printed in the same small type, and
about one-seventh of the thickness, you would have the sum total of the
printed matter which Harvey contributed to our literature. And yet
in that sum total was contained, I may say, the materials of two
revolutions in as many of the main branches of biological science. If
Harvey's published labours can be condensed into so small a compass, you
must recollect that it is not because he did not do a great deal more.
We know very well that he did accumulate a very considerable number of
observations on the most varied topics of medicine, surgery, and natural
history. But, as I mentioned to you just now, Harvey, for a time, took
the royal side in the domestic quarrel of the Great Rebellion, as it
is called; and the Parliament, not unnaturally resenting that action of
his, sent soldiers to seize his papers. And while I